An indoor unit of an air conditioner installed on a ceiling has conventionally been known. In the field of the indoor unit of this type, an indoor unit having the function of removing dust trapped on a filter member has been known. Patent Document 1 discloses an indoor unit of this type.
Specifically, the indoor unit of Patent Document 1 includes, as a structure for removing dust on an air filter, a drive unit, a rotating brush, a collecting case, and a suction device. The air filter is in the shape of a disc, and traps dust contained in the air flowing into the unit through a suction grille. The air filter is provided with teeth formed on the periphery of a frame thereof. The drive unit includes a gear engaged with the teeth of the frame of the air filter. The rotating brush is configured to remove the dust from the air filter, and is in contact with the air filter at the tip thereof. The collecting case accommodates the rotating brush therein, and collects the dust removed by the rotating brush. The suction device is configured to suck and collect the dust fell in the collecting case.
In this indoor unit, the air filter rotates when the drive unit is operated, and the dust adhered to the air filter is removed by the rotating brush. The dust removed from the air filter falls in the collecting case, and the dust in the collecting case is sucked and collected by the suction device.
In the conventional indoor unit of the air conditioner, it has been known that the filter member is lifted/lowered relative to a casing together with a suction grille member provided on a bottom surface of the casing for easy cleaning of the filter member. The indoor unit of this type is disclosed by, for example, Patent Document 2.    Patent Document 1: Published Japanese Patent Application No. 2006-71121    Patent Document 2: Published Japanese Patent Application No. 2004-84998